The present invention relates to image enhancing apparatus and particularly to such apparatus suitable for use with a conventional video recorder for improving sharpness and detail aspects of video recording.
Many video recording devices employ a "coring" circuit for eliminating noise in the signal during playback. High frequency, low amplitude information is assumed to be noise and is attenuated, but unfortunately considerable picture detail can be lost in the process. The resultant video picture has a flat look which may include transitions or edges but with much of the detail lacking. When a recording is made from a TV broadcast that is lacking in sharpness, or when a video tape copy is made from information originating from eight millimeter or sixteen millimeter film or from a second generation tape, sharpness as well as detail may be lacking in a resulting tape copy.
According to my application Ser. No. 183,400 filed Sept. 2, 1980, and entitled "VIDEO DETAIL ENHANCING CIRCUIT", an improved video detail enhancing circuit is provided which introduces enhanced detail into a signal channe by means of clamping large transitions in a video signal and relatively amplifying the smaller transitions representing detail. This circuit, while to a degree efficacious in improving sharpness as well, does not give a degree of independent control over sharpness as may be desired, for example, in recording from a broadcast or a tape copy having poor definition. Circuits are known for emphasizing "edge" transitions in a picture signal by differentiation or the like, but generally do not affect the detail information to a desired degree, and hence do not assist in avoiding the "flat" type of recording described above.